Apparatuses, service networks, and methods for handling plmn-specific parameters for an inter-plmn handover

ABSTRACT

A User Equipment (UE) including a wireless transceiver and a controller is provided. The wireless transceiver performs wireless transmission and reception to and from a first cell of a first Public Land Mobile Network (PLMN) and a second cell of a second PLMN. The controller performs a Location Update (LU) procedure with the second cell via the wireless transceiver in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN, and obtains one or more Session Management (SM), Evolved SM (ESM), or 5GSM parameters of the second PLMN from a Protocol Data Unit (PDU) session modification command, a bearer modification command, or a Packet Data Protocol (PDP) context modification command which is received from the second cell via the wireless transceiver in response to completing the LU procedure caused by the inter-PLMN handover.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. Provisional Application No. 62/655,137, filed on Apr. 9, 2018, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE APPLICATION Field of the Application

The application generally relates to the handling of Public Land Mobile Network (PLMN)-specific parameters, and more particularly, to apparatuses, service networks, and methods for handling PLMN-specific parameters for an inter-PLMN handover.

Description of the Related Art

In a typical mobile communication environment, a User Equipment (UE) (also called Mobile Station (MS)), such as a mobile telephone (also known as a cellular or cell phone), or a tablet Personal Computer (PC) with wireless communications capability, may communicate voice and/or data signals with one or more service networks. The wireless communications between the UE and the service networks may be performed using various cellular technologies, including the Global System for Mobile communications (GSM) technology, the General Packet Radio Service (GPRS) technology, the Enhanced Data rates for Global Evolution (EDGE) technology, the Wideband Code Division Multiple Access (WCDMA) technology, the Code Division Multiple Access 2000 (CDMA-2000) technology, the Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, the Worldwide Interoperability for Microwave Access (WiMAX) technology, the Long Term Evolution (LTE) technology, the LTE-Advanced (LTE-A) technology, the Time Division LTE (TD-LTE) technology, and others.

Particularly, the GSM/GPRS/EDGE technology is also called the 2G cellular technology, the WCDMA/CDMA-2000/TD-SCDMA technology is also called the 3G cellular technology, and the LTE/LTE-A/TD-LTE technology is also called the 4G cellular technology. These cellular technologies have been adopted for use in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is the 5G New Radio (NR). The 5G NR is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, and improving services.

According to the 3GPP specifications and/or requirements in compliance with the 2/3/4/5G cellular technology, a handover of the UE from one cell to another will require the UE to perform a Location Update (LU) procedure, and the handover generally can be completed without the attach procedure, the Protocol Data Unit (PDU) session establishment procedure, the Packet Data Network (PDN) connectivity procedure, or the Packet Data Protocol (PDP) context activation procedure. The same rule may apply to an inter-PLMN handover (i.e., the new cell belongs to a different PLMN) as well.

However, some configurations associated with the new PLMN can only be acquired or provided during the attach procedure, the PDU session establishment procedure, the PDN connectivity procedure, or the PDP context activation procedure. As a result, the LU procedure may not be enough to provide all necessary information to the UE for an inter-PLMN handover.

BRIEF SUMMARY OF THE APPLICATION

In order to solve the aforementioned problem, the present application proposes efficient way of signaling for a UE to request for Mobility Management (MM)/Evolved MM (EMM)/5GMM parameters and Session Management (SM)/Evolved SM (ESM)/5GSM parameters of the new PLMN for an inter-PLMN handover, without the need of the attach procedure, the PDU session establishment procedure, the PDN connectivity procedure, or the PDP context activation procedure.

In a first aspect of the application, a User Equipment (UE) comprising a wireless transceiver and a controller is provided. The wireless transceiver is configured to perform wireless transmission and reception to and from a first cell of a first Public Land Mobile Network (PLMN) and a second cell of a second PLMN. The controller is configured to perform a Location Update (LU) procedure with the second cell via the wireless transceiver in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN, and obtain one or more SM/ESM/5GSM parameters of the second PLMN from a Protocol Data Unit (PDU) session modification command, a bearer modification command, or a Packet Data Protocol (PDP) context modification command which is received from the second cell via the wireless transceiver in response to completing the LU procedure caused by the inter-PLMN handover.

In a second aspect of the application, a method for handling PLMN-specific parameters for an inter-PLMN handover, executed by a UE communicatively connected to a first cell of a first PLMN and a second cell of a second PLMN, is provided. The method comprises the steps of: performing an LU procedure with the second cell in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN; and obtaining one or more SM/ESM/5GSM parameters of the second PLMN from a PDU session modification command, a bearer modification command, or a PDP context modification command which is received from the second cell in response to completing the LU procedure caused by the inter-PLMN handover.

In a third aspect of the application, a method for handling PLMN-specific parameters for an inter-PLMN handover, executed by a UE communicatively connected to a first cell of a first PLMN and a second cell of a second PLMN, is provided. The method comprises the steps of: performing an LU procedure with the second cell in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN; and applying one or more SM/ESM/5GSM parameters of the first PLMN for the second PLMN in response to completing the LU procedure caused by the inter-PLMN handover.

Other aspects and features of the present application will become apparent to those with ordinarily skill in the art upon review of the following descriptions of specific embodiments of the UEs, service networks, and the methods for handling PLMN-specific parameters for an inter-PLMN handover.

BRIEF DESCRIPTION OF DRAWINGS

The application can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a block diagram of a wireless communication environment according to an embodiment of the application;

FIG. 2 is a block diagram illustrating the UE 110 according to an embodiment of the application;

FIG. 3 is a message sequence chart illustrating the method for handling PLMN-specific parameters for an inter-PLMN handover according to an embodiment of the application;

FIG. 4 is a message sequence chart illustrating the method for handling PLMN-specific parameters for an inter-PLMN handover according to another embodiment of the application; and

FIG. 5 is a message sequence chart illustrating the method for handling PLMN-specific parameters for an inter-PLMN handover according to yet another embodiment of the application.

DETAILED DESCRIPTION OF THE APPLICATION

The following description is made for the purpose of illustrating the general principles of the application and should not be taken in a limiting sense. It should be understood that the embodiments may be realized in software, hardware, firmware, or any combination thereof. The terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

FIG. 1 is a block diagram of a wireless communication environment according to an embodiment of the application.

As shown in FIG. 1, the wireless communication environment 100 includes a User Equipment (UE) 110 and two service networks 120 and 130, wherein the UE 110 may be wirelessly and communicatively connected to one or both of the service networks 120 and 130, and the service networks 120 and 130 belong to different Public Land Mobile Networks (PLMNs).

The UE 110 may be a feature phone, a smartphone, a panel Personal Computer (PC), a laptop computer, or any wireless communication device supporting at least the cellular technologies utilized by the service networks 120 and 130.

Specifically, the service network 120 may include an access network 121 and a core network 122. The access network 121 is responsible for processing radio signals, terminating radio protocols, and connecting the UE 110 with the core network 122, while the core network 122 is responsible for performing mobility management, network-side authentication, and interfaces with a public/external data network (e.g., the Internet). In particular, the core network 122 also coordinates the operations of the access network 121 for performing the method for handling PLMN-specific parameters for an inter-PLMN handover of the UE 110.

Similarly, the service network 130 may include an access network 131 and a core network 132. The access network 131 is responsible for processing radio signals, terminating radio protocols, and connecting the UE 110 with the core network 132, while the core network 132 is responsible for performing mobility management, network-side authentication, and interfaces with a public/external data network (e.g., the Internet). In particular, the core network 132 also coordinates the operations of the access network 131 for performing the method for handling PLMN-specific parameters for an inter-PLMN handover of the UE 110.

For example, if the service network 120 or 130 is a 2G system, e.g., a GSM/EDGE/GPRS system, the access network 121 or 131 may be a Base Station Subsystem (BSS), and the core network 122 or 132 may be a GPRS core. A BSS may include at least a Base Transceiver Station (BTS) and a Base Station Controller (BSC), wherein each BTS may form a cell for providing mobile services to the UE 110. A GPRS core may include at least a Home Location Register (HLR), at least a Serving GPRS Support Node (SGSN), at least a Gateway GPRS Support Node (GGSN), wherein each of the HLR, SGSN, and GGSN may be implemented as a network element on a dedicated hardware (e.g., a controller, such as a processor, and/or a storage device, such as memory), or as a software instance running on a dedicated hardware.

If the service network 120 or 130 is a 3G system, e.g., a WCDMA system, the access network 121 or 131 may be a Universal Terrestrial Radio Access Network (UTRAN), and the core network 122 or 132 may be a GPRS core. A UTRAN may include at least one BS and at least one Radio Network Controller (RNC), wherein each BS may form a cell for providing mobile services to the UE 110. A GPRS core may include at least an MSC, at least an HLR, at least an SGSN, and at least a GGSN, wherein each of the HLR, SGSN, and GGSN may be implemented as a network element on a dedicated hardware (e.g., a controller, such as a processor, and/or a storage device, such as memory), or as a software instance running on a dedicated hardware.

If the service network 120 or 130 is a 4G system, e.g., an LTE system, the access network 121 or 131 may be an Evolved-UTRAN (E-UTRAN), and the core network 122 or 132 may be an Evolved Packet Core (EPC). An E-UTRAN may include at least an evolved NodeBs (eNB), including macro eNBs, femto eNBs, or pico eNBs, each of which may form a cell for providing mobile services to the UE 110. An EPC may include at least a Home Subscriber Server (HSS), Mobility Management Entity (MME), Serving Gateway (S-GW), Packet Data Network Gateway (PDN-GW or P-GW), wherein each of the HSS, MME, S-GW, and P-GW may be implemented as a network element on a dedicated hardware (e.g., a controller, such as a processor, and/or a storage device, such as memory), or as a software instance running on a dedicated hardware.

If the service network 120 or 130 is a 5G system, e.g., a 5G NR system, the access network 121 or 131 may be a Next Generation Radio Access Network (NG-RAN), and the core network 122 or 132 may be a Next Generation Core Network (NG-CN). A NG-RAN may include one or more gNBs which support high frequency bands (e.g., above 24 GHz), and each gNB may further include one or more Transmission Reception Points (TRPs), wherein each gNB or TRP may be referred to as a 5G cellular station. Some gNB functions may be distributed across different TRPs, while others may be centralized, leaving the flexibility and scope of specific deployments to fulfill the requirements for specific cases. A 5G cellular station may form one or more cells with different Component Carriers (CCs) for providing mobile services to the UE 110. A NG-CN may consist of various network functions, including at least an AMF, a Session Management Function (SMF), a User Plane Function (UPF), a Policy Control Function (PCF), an Application Function (AF), and an Authentication Server Function (AUSF), wherein each network function may be implemented as a network element on a dedicated hardware (e.g., a controller, such as a processor, and/or a storage device, such as memory), or as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.

The AMF provides UE-based authentication, authorization, mobility management, etc. The SMF is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF for data transfer. If a UE has multiple sessions, different SMFs may be allocated to each session to manage them individually and possibly provide different functions per session.

The AF provides information on the packet flow to PCF responsible for policy control in order to support Quality of Service (QoS). Based on the information, the PCF determines policies about mobility and session management to make the AMF and the SMF operate properly. The AUSF stores data for authentication of UEs, while the UDM stores subscription data of UEs.

Although not shown, the service networks 120 and 130 may support interworking with specific communication interface(s). For example, if the service networks 120 and 130 are an LTE system and a 5G NR system, there may be an N26 interface connecting the MME of the LTE system and the AMF of the 5G NR system.

It should be understood that wireless communication environment 100 is for illustrative purposes only and is not intended to limit the scope of the application. For example, the application could be applied to other cellular technologies, such as a future enhancement of the 5G NR technology.

FIG. 2 is a block diagram illustrating the UE 110 according to an embodiment of the application.

As shown in FIG. 2, the UE 110 may include a wireless transceiver 10, a controller 20, a storage device 30, a display device 40, and an Input/Output (I/O) device 50.

The wireless transceiver 10 is configured to perform wireless transmission and reception to and from the cell(s) formed by the cellular station(s) of one or both of the access networks 121 and 131.

Specifically, the wireless transceiver 10 may include a Radio Frequency (RF) device 11, a baseband processing device 12, and antenna(s) 13, wherein the antenna(s) 13 may include one or more antennas for beamforming.

The baseband processing device 12 is configured to perform baseband signal processing and control the communications between subscriber identity card(s) (not shown) and the RF device 11. The baseband processing device 12 may contain multiple hardware components to perform the baseband signal processing, including Analog-to-Digital Conversion (ADC)/Digital-to-Analog Conversion (DAC), gain adjusting, modulation/demodulation, encoding/decoding, and so on.

The RF device 11 may receive RF wireless signals via the antenna(s) 13, convert the received RF wireless signals to baseband signals, which are processed by the baseband processing device 12, or receive baseband signals from the baseband processing device 12 and convert the received baseband signals to RF wireless signals, which are later transmitted via the antenna(s) 13. The RF device 11 may also contain multiple hardware devices to perform radio frequency conversion. For example, the RF device 11 may include a mixer to multiply the baseband signals with a carrier oscillated in the radio frequency of the supported cellular technologies, wherein the radio frequency may be 900 MHz, 1800 MHz, or 1900 MHz utilized in the 2G (e.g., GSM/GPRS/EDGE) systems, or 900 MHz, 1900 MHz, or 2100 MHz utilized in 3G (e.g., WCDMA) systems, or 900 MHz, 2100 MHz, or 2.6 GHz utilized in 4G (e.g., LTE) systems, or any radio frequency (e.g., 30 GHz˜300 GHz for mmWave) utilized in 5G (e.g., NR) systems, or another radio frequency, depending on the cellular technology in use.

The controller 20 may be a general-purpose processor, a Micro Control Unit (MCU), an application processor, a Digital Signal Processor (DSP), a Graphics Processing Unit (GPU), a Holographic Processing Unit (HPU), a Neural Processing Unit (NPU), or the like, which includes various circuits for providing the functions of data processing and computing, controlling the wireless transceiver 10 for wireless communications with the service networks 120 and 130, storing and retrieving data (e.g., program code) to and from the storage device 30, sending a series of frame data (e.g. representing text messages, graphics, images, etc.) to the display device 40, and receiving user inputs or outputting signals via the I/O device 50.

In particular, the controller 20 may coordinate the aforementioned operations of the wireless transceiver 10, the storage device 30, the display device 40, and the I/O device 50 for performing the method for handling PLMN-specific parameters for an inter-PLMN handover.

In another embodiment, the controller 20 may be incorporated into the baseband processing device 12, to serve as a baseband processor.

As will be appreciated by persons skilled in the art, the circuits of the controller 20 will typically include transistors that are configured in such a way as to control the operation of the circuits in accordance with the functions and operations described herein. As will be further appreciated, the specific structure or interconnections of the transistors will typically be determined by a compiler, such as a Register Transfer Language (RTL) compiler. RTL compilers may be operated by a processor upon scripts that closely resemble assembly language code, to compile the script into a form that is used for the layout or fabrication of the ultimate circuitry. Indeed, RTL is well known for its role and use in the facilitation of the design process of electronic and digital systems.

The storage device 30 may be a non-transitory machine-readable storage medium, including a memory, such as a FLASH memory or a Non-Volatile Random Access Memory (NVRAM), or a magnetic storage device, such as a hard disk or a magnetic tape, or an optical disc, or any combination thereof for storing data (e.g., PLMN-specific parameters), instructions, and/or program code of applications, communication protocols, and/or the method for handling PLMN-specific parameters for an inter-PLMN handover.

The display device 40 may be a Liquid-Crystal Display (LCD), a Light-Emitting Diode (LED) display, an Organic LED (OLED) display, or an Electronic Paper Display (EPD), etc., for providing a display function. Alternatively, the display device 40 may further include one or more touch sensors disposed thereon or thereunder for sensing touches, contacts, or approximations of objects, such as fingers or styluses.

The I/O device 50 may include one or more buttons, a keyboard, a mouse, a touch pad, a video camera, a microphone, and/or a speaker, etc., to serve as the Man-Machine Interface (MMI) for interaction with users.

It should be understood that the components described in the embodiment of FIG. 2 are for illustrative purposes only and are not intended to limit the scope of the application. For example, the UE 110 may include more components, such as a power supply, and/or a Global Positioning System (GPS) device, wherein the power supply may be a mobile/replaceable battery providing power to all the other components of the UE 110, and the GPS device may provide the location information of the UE 110 for use by some location-based services or applications. Alternatively, the UE 110 may include fewer components. For example, the UE 110 may not include the display device 40 and/or the I/O device 50.

FIG. 3 is a message sequence chart illustrating the method for handling PLMN-specific parameters for an inter-PLMN handover according to an embodiment of the application.

In this embodiment, the method for handling PLMN-specific parameters for an inter-PLMN handover is applied to and executed by a UE (e.g., the UE 110) and two service networks belonging to different PLMNs (e.g., the service network 120 or 130).

To begin with, the UE performs a registration procedure with the service network 120 (step S301).

In one embodiment, the registration procedure may be a registration procedure for a 5G system, wherein the Registration Request message may include a 5G System (5GS) registration type Information Element (IE) set to “initial registration”.

In another embodiment, the registration procedure may be an attach procedure for a 2/3/4G system.

Next, the UE 110 approaches the service network 130 (step S302), and sends a Measurement Report message including the measured result of the cell of the service network 130 to the service network 120 (step S303).

Assuming that the measured result included in the Measurement Report message satisfies the handover condition(s) (e.g., the signal quality of the source cell is below a certain threshold, and the signal quality of the target cell is greater than a certain threshold), the service network 120 decides to handover the UE 110 to the service network 130 (step S304), and in response to the decision, sends a Handover Command to the UE 110 (step S305). The Handover Command may include configurations associated with the service network 130, e.g., the information of the target cell for the handover.

When receiving the Handover Command, the UE 110 switches from the source cell (i.e., a cell of the service network 120) to the target cell (i.e., a cell of the service network 130) to complete the handover (step S306).

Since the location area (e.g., Tracking Area (TA), or Routing Area (RA)) is changed due to the change of the PLMN after the completion of the handover, the UE 110 performs a Location Update (LU) procedure with the service network 130.

Specifically, during the LU procedure, the UE 110 sends an LU request including an indication of the inter-PLMN handover to the service network 130 (step S307), and the service network 130 replies to the UE 110 with an LU accept which may include one or more MM/EMM/5GMM parameters of the PLMN (denoted as PLMN-2 in FIG. 3) to which the service network 130 belongs (step S308).

In one embodiment, if the service network 130 is a 5G system, the LU procedure may be a Registration procedure, and accordingly, the LU request may be a Registration Request message including a 5GS registration type IE set to “mobility registration updating”, and the LU accept may be a Registration Accept message.

In another embodiment, if the service network 130 is a 4G system, the LU procedure may be a Tracking Area Update (TAU) procedure, and accordingly, the LU request may be a Tracking Area Update Request message, and the LU accept may be a Tracking Area Update Accept message.

In yet another embodiment, if the service network 130 is a 2/3G system, the LU procedure may be a Routing Area Update (RAU) procedure, and accordingly, the LU request may be a Routing Area Update Request message, and the LU accept may be a Routing Area Update Accept message.

Upon completion of the LU procedure caused by the inter-PLMN handover, the service network 130 sends a Protocol Data Unit (PDU) session modification command, a bearer modification command, or a Packet Data Protocol (PDP) context modification command to the UE 110 in response to the indication of the inter-PLMN handover, wherein the PDU session modification command, the bearer modification command, or the PDP context modification command includes one or more Session Management (SM)/Evolved SM (ESM)/5GSM parameters of the PLMN (denoted as PLMN-2 in FIG. 3) to which the service network 130 belongs (step S309), and the method ends.

In other words, the indication of the inter-PLMN handover in the LU request serves to trigger the service network 130 to send the SM/ESM/5GSM parameters of PLMN-2 in a PDU session modification command, a bearer modification command, or a PDP context modification command upon completion of the LU procedure.

Specifically, which one of the PDU session modification command, the bearer modification command, and the PDP context modification command is sent depends on the cellular technology utilized by the service network 130.

For example, if the service network 130 is a 5G system, the PDU session modification command is sent, and more particularly, the PDU session modification command may be a PDU Session Modification Command message.

If the service network 130 is a 4G system, the bearer modification command is sent, and more particularly, the bearer modification command may be a Modify EPS (Evolved Packet System) Bearer Context Request message.

If the service network 130 is a 2/3G system, the PDP context modification command is sent, and more particularly, the PDP context modification command may be a Modify PDP Context Request message (e.g., for a MS-initiated PDP context modification procedure) or a Modify PDP Context Accept message (e.g., for a NW-initiated PDP context modification procedure).

The SM/ESM/5GSM parameters may include at least one of: configuration associated with a Narrow Band-Internet of Things (NB-IoT) rate control, and configuration associated with a Packet-Switched (PS) data off feature.

Please note that detailed descriptions of the 5G Registration procedure and the PDU session modification procedure are omitted herein for brevity since they are beyond the scope of the present application, and reference may be made to the 3GPP TS 24.501, release 15.

Detailed descriptions of the 4G attach procedure, the TAU procedure, and the bearer modification procedure are omitted herein for brevity since they are beyond the scope of the present application, and reference may be made to the 3GPP TS 24.301, release 15.

Detailed descriptions of the 2/3G attach procedure, the RAU procedure, and the PDP context modification procedure are omitted herein for brevity since they are beyond the scope of the present application, and reference may be made to the 3GPP TS 24.008, release 15.

FIG. 4 is a message sequence chart illustrating the method for handling PLMN-specific parameters for an inter-PLMN handover according to another embodiment of the application.

In this embodiment, steps S401 to S406 are the same as steps S301 to S306, and detailed descriptions of steps S401 to S406 are omitted for brevity.

Subsequent to step S406, the UE performs an LU procedure with the service network 130.

Specifically, during the LU procedure, the UE 110 sends an LU request to the service network 130 (step S407), and the service network 130 replies to the UE 110 with an LU accept which may include one or more MM/EMM/5GMM parameters of the PLMN (denoted as PLMN-2 in FIG. 4) to which the service network 130 belongs (step S408).

Please note that the LU request in step S407 is different from the LU request in step S307, because the LU request in step S407 does not include an indication of the inter-PLMN handover.

Detailed descriptions of various embodiments of the LU request and the LU accept are omitted herein for brevity, and reference may be made to the embodiments described in FIG. 3.

Upon completion of the LU procedure caused by the inter-PLMN handover, the UE 110 sends to the service network 130 a request for SM/ESM/5GSM parameters of the PLMN (denoted as PLMN-2 in FIG. 4) to which the service network 130 belongs (step S409).

Specifically, the request may be a PDU Session Modification Request message if the service network 130 is a 5G system, or may be a Bearer Resource Modification Request message if the service network 130 is a 4G system, or may be a Modify PDP Context Request message if the service network 130 is a 2/3G system.

When receiving the request, the service network 130 replies to the UE 110 with a PDU session modification command, a bearer modification command, or a PDP context modification command which includes the SM/ESM/5GSM parameters of the PLMN (denoted as PLMN-2 in FIG. 4) to which the service network 130 belongs (step S410), and the method ends.

In other words, the request in step S409 serves to trigger the service network 130 to send the SM/ESM/5GSM parameters of PLMN-2 in a PDU session modification command, a bearer modification command, or a PDP context modification command.

Specifically, which one of the PDU session modification command, the bearer modification command, and the PDP context modification command is sent depends on the cellular technology utilized by the service network 130. Reference may be made to the embodiments described in FIG. 3 for detailed descriptions of the PDU session modification command, the bearer modification command, and the PDP context modification command.

FIG. 5 is a message sequence chart illustrating the method for handling PLMN-specific parameters for an inter-PLMN handover according to an embodiment of the application.

In this embodiment, the method for handling PLMN-specific parameters for an inter-PLMN handover is applied to and executed by a UE (e.g., the UE 110) which is being handed over from one PLMN to another.

To begin with, the UE performs a registration procedure with the service network 120 (step S501).

In one embodiment, the registration procedure may be a registration procedure for a 5G system, wherein the Registration Request message may include a 5GS registration type IE set to “initial registration”, and the Registration Accept message may include one or more SM/ESM/5GSM parameters of the PLMN (denoted as PLMN-1 in FIG. 5) to which the service network 120 belongs.

In another embodiment, the registration procedure may be an attach procedure for a 2/3/4G system, wherein the Attach Accept message may include one or more SM/ESM/5GSM parameters of the PLMN (denoted as PLMN-1 in FIG. 5) to which the service network 120 belongs.

Alternatively, the UE 110 may additionally perform a PDU session establishment procedure, a PDN connectivity procedure, or a PDP context activation procedure (depending on the cellular technology utilized by the service network 120) with the service network 120 to obtain more SM/ESM/5GSM parameters of the PLMN (denoted as PLMN-1 in FIG. 5) to which the service network 120 belongs.

Next, the UE 110 approaches the service network 130 (step S502), and sends a Measurement Report message including the measured result of the cell of the service network 130 to the service network 120 (step S503).

Assuming that the measured result included in the Measurement Report message satisfies the handover condition(s) (e.g., the signal quality of the source cell is below a certain threshold, and the signal quality of the target cell is greater than a certain threshold), the service network 120 decides to hand over the UE 110 to the service network 130 (step S504), and in response to the decision, sends a Handover Command to the UE 110 (step S505). The Handover Command may include configurations associated with the service network 130, e.g., the information of the target cell for the handover.

When receiving the Handover Command, the UE 110 switches from the source cell (i.e., a cell of the service network 120) to the target cell (i.e., a cell of the service network 130) to complete the handover (step S506).

Since the location area (e.g., TA, or RA) is changed due to the change of the PLMN after the completion of the handover, the UE 110 performs an LU procedure with the service network 130.

Specifically, during the LU procedure, the UE 110 sends an LU request to the service network 130 (step S507), and the service network 130 replies to the UE 110 with an LU accept which may include one or more MM/EMM/5GMM parameters of the PLMN to which the service network 130 belongs (step S508).

Please note that the LU request in step S507 is different from the LU request in step S307, because the LU request in step S507 does not include an indication of the inter-PLMN handover.

Detailed descriptions of various embodiments of the LU request and the LU accept are omitted herein for brevity, and reference may be made to the embodiments described in FIG. 3.

Upon completion of the LU procedure caused by the inter-PLMN handover, the UE 110 applies the SM/ESM/5GSM parameters of PLMN-1 for PLMN-2 (step S509), and the method ends.

In one embodiment, the UE 110 may apply the SM/ESM/5GSM parameters of PLMN-1 for PLMN-2, by reusing the current values of the SM/ESM/5GSM parameters of PLMN-1 for PLMN-2. That is, the SM/ESM/5GSM parameters of PLMN-2 are set to the current values of the SM/ESM/5GSM parameters of PLMN-1.

In another embodiment, the UE 110 may apply the SM/ESM/5GSM parameters of PLMN-1 for PLMN-2, by using the default values of the SM/ESM/5GSM parameters of PLMN-1 for PLMN-2. That is, the SM/ESM/5GSM parameters of PLMN-2 are set to the default values of the SM/ESM/5GSM parameters of PLMN-1, wherein the default values may be standardized values (i.e., the default values defined in the 3GPP specifications), or may be predefined values stored in a Management Object (MO) or a Subscriber Identity Module (SIM)/Universal SIM (USIM) in the UE 110.

In view of the forgoing embodiments, it should be appreciated that the present application proposes efficient way of signaling for a UE to request for MM/EMM/5GMM parameters and SM/ESM/5GSM parameters of the new PLMN for an inter-PLMN handover, without the need of the attach procedure, the PDU session establishment procedure, the PDN connectivity procedure, or the PDP context activation procedure. Advantageously, the UE may obtain all necessary information to support the communication features with the new PLMN after the handover.

While the application has been described by way of example and in terms of preferred embodiment, it should be understood that the application is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this application. Therefore, the scope of the present application shall be defined and protected by the following claims and their equivalents.

Use of ordinal terms such as “first”, “second”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having the same name (but for use of the ordinal term) to distinguish the claim elements. 

What is claimed is:
 1. A User Equipment (UE), comprising: a wireless transceiver, configured to perform wireless transmission and reception to and from a first cell of a first Public Land Mobile Network (PLMN) and a second cell of a second PLMN; and a controller, configured to perform a Location Update (LU) procedure with the second cell via the wireless transceiver in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN, and obtain one or more Session Management (SM), Evolved SM (ESM), or 5GSM parameters of the second PLMN from a Protocol Data Unit (PDU) session modification command, a bearer modification command, or a Packet Data Protocol (PDP) context modification command which is received from the second cell via the wireless transceiver in response to completing the LU procedure caused by the inter-PLMN handover.
 2. The UE of claim 1, wherein the LU procedure comprises sending an LU request comprising an indication of the inter-PLMN handover to the second cell via the wireless transceiver, and the indication of the inter-PLMN handover triggers the second PLMN to send the PDU session modification command, the bearer modification command, or the PDP context modification command via the second cell upon completion of the LU procedure.
 3. The UE of claim 1, wherein the controller is further configured to send a request for the SM, ESM, or 5GSM parameters to the second cell via the wireless transceiver upon completing the LU procedure, prior to receiving the PDU session modification command, the bearer modification command, or the PDP context modification command from the second cell via the wireless transceiver.
 4. The UE of claim 3, wherein the request is a PDU Session Modification Request message in response to the second cell utilizing a 5G cellular technology, or a Bearer Resource Modification Request message in response to the second cell utilizing a 4G cellular technology, or a Modify PDP Context Request message in response to the second cell utilizing a 2G or 3G cellular technology.
 5. The UE of claim 1, wherein, in response to the second cell utilizing a 5G cellular technology, the LU procedure is a Registration procedure with a 5G System (5GS) registration type Information Element (IE) set to “mobility registration updating” and the PDU session modification command is a PDU Session Modification Command message.
 6. The UE of claim 1, wherein, in response to the second cell utilizing a 4G cellular technology, the LU procedure is a Tracking Area Update (TAU) procedure and the bearer modification command is a Modify EPS (Evolved Packet System) Bearer Context Request message.
 7. The UE of claim 1, wherein, in response to the second cell utilizing a 2G or 3G cellular technology, the LU procedure is a Routing Area Update (RAU) procedure and the PDP context modification command is a Modify PDP Context Request message or a Modify PDP Context Accept message.
 8. The UE of claim 1, wherein the SM, ESM, or 5GSM parameters comprise at least one of: configuration associated with a Narrow Band-Internet of Things (NB-IoT) rate control; and configuration associated with a Packet-Switched (PS) data off feature.
 9. The UE of claim 1, wherein the controller is further configured to obtain one or more Mobility Management (MM), Evolved MM (EMM), or 5GMM parameters of the second PLMN during the LU procedure.
 10. A method for handling Public Land Mobile Network (PLMN)-specific parameters for an inter-PLMN handover, executed by a User Equipment (UE) communicatively connected to a first cell of a first PLMN and a second cell of a second PLMN, the method comprising: performing a Location Update (LU) procedure with the second cell in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN; and obtaining one or more SM, Evolved SM (ESM), or 5GSM parameters of the second PLMN from a Protocol Data Unit (PDU) session modification command, a bearer modification command, or a Packet Data Protocol (PDP) context modification command which is received from the second cell in response to completing the LU procedure caused by the inter-PLMN handover.
 11. The method of claim 10, wherein the LU procedure comprises sending an LU request comprising an indication of the inter-PLMN handover to the second cell, and the indication of the inter-PLMN handover triggers the second PLMN to send the PDU session modification command, the bearer modification command, or the PDP context modification command via the second cell upon completion of the LU procedure.
 12. The method of claim 10, further comprising: sending a request for the SM, ESM, or 5GSM parameters to the second cell upon completing the LU procedure, prior to receiving the PDU session modification command, the bearer modification command, or the PDP context modification command from the second cell.
 13. The method of claim 12, wherein the request is a PDU Session Modification Request message in response to the second cell utilizing a 5G cellular technology, or a Bearer Resource Modification Request message in response to the second cell utilizing a 4G cellular technology, or a Modify PDP Context Request message in response to the second cell utilizing a 2G or 3G cellular technology.
 14. The method of claim 10, wherein, in response to the second cell utilizing a 5G cellular technology, the LU procedure is a Registration procedure with a 5G System (5GS) registration type Information Element (IE) set to “mobility registration updating” and the PDU session modification command is a PDU Session Modification Command message.
 15. The method of claim 10, wherein, in response to the second cell utilizing a 4G cellular technology, the LU procedure is a Tracking Area Update (TAU) procedure and the bearer modification command is a Modify EPS Bearer Context Request message.
 16. The method of claim 10, wherein, in response to the second cell utilizing a 2G or 3G cellular technology, the LU procedure is a Routing Area Update (RAU) procedure and the PDP context modification command is a Modify PDP Context Request message or a Modify PDP Context Accept message.
 17. The method of claim 10, wherein the SM, ESM, or 5GSM parameters comprise at least one of: configuration associated with a Narrow Band-Internet of Things (NB-IoT) rate control; and configuration associated with a Packet-Switched (PS) data off feature.
 18. A method for handling Public Land Mobile Network (PLMN)-specific parameters for an inter-PLMN handover, executed by a User Equipment (UE) communicatively connected to a first cell of a first PLMN and a second cell of a second PLMN, the method comprising: performing a Location Update (LU) procedure with the second cell in response to an inter-PLMN handover of the UE from the first cell of the first PLMN to the second cell of the second PLMN; and applying one or more Session Management (SM), Evolved SM (ESM), or 5GSM parameters of the first PLMN for the second PLMN in response to completing the LU procedure caused by the inter-PLMN handover.
 19. The method of claim 18, wherein the applying of the SM, ESM, or 5GSM parameters of the first PLMN for the second PLMN comprises: reusing current values of the SM, ESM, or 5GSM parameters of the first PLMN for the second PLMN.
 20. The method of claim 18, wherein the applying of the SM, ESM, 5GSM parameters of the first PLMN for the second PLMN comprises: using default values of the SM, ESM, 5GSM parameters of the first PLMN for the second PLMN. 